You may get used to it, you may not. Some tastes definitely need time to adjust to. For me, it was Marmite. First time I had Marmite, I thought I was going to vomit. Second time, not so bad. Third time, hey, this stuff is good! Now, I'm addicted to it.
So, since I came from the Marmite perspective, fish sauce has never been much of a challenge to me (I absolutely
love nuoc mam[/i], and have been known to drink it straight out of the bottle to sate a salt craving.)
All I can say is, keep trying it. If you don't take to it, so what? Plenty of other good food to go around.